1. Field of the Invention
The present invention relates to a heating furnace system to receive a stream of thin, continuously cast workpieces and supply such workpieces at a desired rolling temperature to a hot rolling mill, more particularly the present invention relates to such a heating furnace system having a greatly reduced floor space requirement while utilizing ancillary continuous casting and rolling mill facilities to increased limit of capacities and accommodating necessary downtimes for maintenance of such facilities.
2. Description of the Prior Art
The continuous casting of thick, e.g., 8 inches, slab workpieces gave rise to possible direct rolling of the workpieces by the use of an intermediate furnace to control the temperature of the workpiece entering the rolling mill. In recent years, the discovery of techniques that allow continuous casting of thin relatively wide workpieces of the order of between 2 and 4 inches thick and between 24 and 120 inches wide, contribute to numerous beneficial advantages that are an advancement in the art. There are disadvantages arising out of the reheat furnace necessary to allow the direct rolling of the thin cast workpieces as well as more traditional continuously cast workpieces that can be greater than 4 inches thick and may range up to 10 inches thick. The thin cast workpieces can be processed in a hot rolling mill to produce hot strip product or steel plate. The thicker continuously cast product ranging between 4 and 10 inches can be rolled in a hot rolling mill to produce a hot rolled plate product or if desired more extensive hot rolling can be carried out to form a hot rolled strip. As the cast workpiece emerges from the casting facility, a torch or other cutting device subdividing the casting to form workpieces of a finite length typically approximately 80 to 150 feet long with the width varying between 24 and 120 inches. An example of a facility to direct roll such continuous cast workpieces is illustrated diagrammatically in FIG. 1. The workpiece emerging at the discharge end E of a continuous caster is feed directly in a reheat furnace F. As disclosed in my U.S. Pat. Nos. 4,991,276 and 5,082,047, flexible driven rollers may be used to convey as well as guide the thin cast workpieces along the entire length of the furnace during the reheating process. The required length for such a furnace ranges from at least 300 feet up to 750 feet to heat a required number of continuously cast workpieces when the workpieces each measures 80 to 150 feet long. Because the reheating process is continuous and reheat time is finite for each workpiece multiple workpieces must be heated in the furnace at any given time. Not only must the ends of the workpieces be separated from one another in the furnace to allow orderly processing in the rolling mill M but also a time buffer is needed when the rolling operation is interrupted by the need to service the rolling mill equipment such as conventional roll changing. During such downtime for servicing operations, the workpiece can be oscillated forwardly and backwardly by the driven rollers in the furnace or the speed of the emerging casting from the caster must be slowed; both such measures while providing a time buffer have severe limitations.
The facility illustrated in FIG. 1 requires considering real estate as well as an inordinately long building structure to house the facility. Given that the furnace in FIG. 1 must be 700 feet long there must be also provided an additional distance at each end of the furnace of at least 30 feet for entry and delivery tables to receive the casting at the cutting device from the caster and to deliver the workpiece at the rolling temperate to the first stand of the rolling mill. In a facility of the type illustrated in FIG. 1, the capital investment represented by the rolling mill facility can be utilized to a far greater extent by the supply of workpieces from a plurality of casters. However, the castings emerging from the various casters can not be supplied to the same entry pass-line to a furnace.
An arrangement shown in FIG. 2 is also known in the art and provides separate continuous casters having delivery ends E that supply workpieces cut to finite length by torches T to separate reheat furnaces F each required to have a length of about 700 feet to achieve the required workpiece reheat operations. Furnace sections S.sub.1 and S.sub.2 are mounted on a track system to allow a lateral shuttle transfer of the furnace sections into alignment with the entry table for the rolling mill M for a time sufficient to empty the furnace of the workpiece and then laterally reposition the furnace section so that the other such furnace is positioned for feeding a workpiece into the entry table of the rolling mill. The addition of the shuttle furnace sections increases the requirement for floor space to accommodate the length of the shuttle furnace which must be slightly greater than the length of the workpiece. For example, when the workpiece is 150 feet long, the shuttle furnace section will be approximately 155 feet long. The shuttle furnace in this instance severs the important function of receiving and holding a workpiece at a desired rolling temperature while a workpiece is discharged from the other of the furnace sections and at the same time accommodates the requirement to bring workpieces from laterally spaced casters into an alignment with a single rolling mill installation. The present invention seeks not only to reduce the required amount of real estate, but also the expense for building structure to house reheat furnace equipment for direct rolling of continuously cast thin workpieces.
Accordingly, it is an object of the present invention to provide a furnace arrangement that will minimize the real estate and building requirements necessary to house the workpiece reheat furnace facilities for direct rolling of the workpieces produced by one or more continuous casting facilities.
It is another object of the present invention to provide a furnace arrangement for reheating thin, continuously cast workpieces for processing in a hot rolling mill in which two streams of continuously cast workpieces are merged seriatim to a holding furnace to at least minimize loss of latent heat of the continuous casting process and deliver the workpiece in a serial fashion to a reheat furnace for heating workpieces to a desired rolling temperature at the entry side of a hot rolling mill.
It is further object of the present invention to provide a reheat furnace for receiving a succession of continuously cast workpieces having a finite length and a hot core in which each workpiece is held at a preselected one of a plurality of vertically spaced sites within a furnace enclosure until such time as such workpiece can be discharged upon attaining a desired elevated temperature suitable for hot rolling operations.